DG's method is great for a business type machine - usually just the OS, an office suite, printer drivers and a few specialist oddments to reinstall.
However, a domestic machine will have a bucketfull of applications - mine does my home office, plus my photo handling plus my music collection, plus a load of other stuff that I use occasionally and always forget in a reload - there are about 4 folders on my desktop each with several applications, some of which (like the bank security) have to be remembered. Rather than one afternoon, its usually several day to get the lot back in.
I find that a regular shot of clearing out with something like Malwarebytes, then a disc clean (hiding in accessories/system tools somewhere, using the "get rid of the old registry backups" option), then a registry clean followed by a defrag (I like Auslogics programs for both these) keeps the system nice and sprightly. Assuming it still works (i.e. no harm done), I use a partition cloning program to make a backup of my C: drive. Easeus, I have also used Paragon. Should a disaster occur, it takes 25 minutes to reload the entire system onto a new drive, provided that this clone is not too old, it just needs a little time then for all of the updates to be re-done. This is OS, all of the programs, and all of the settings including favourite/bookmark lists and stored passwords. , at least, the ones up to the time of the backup.
